SustainSea: cutting maritime CO₂ emissions with wind power

Backed by a €4.1 million grant from the EU’s Innovation Fund, the SustainSea project is cutting fuel consumption and emissions from cargo ships by harnessing the wind. Specifically, it is retrofitting five large vessels with up to 26-metre-high eSAIL® suction sails developed by Spanish deeptech firm bound4blue, a leader in clean shipping and wind-assisted propulsion technology. This innovative suction sail operates in a similar way to an aircraft wing placed upright, generating lift and thrust from the wind. 

Specifically, the project’s sail system is able to ensure that the airflow remains attached to the sail, dramatically boosting lift and generating thrust directly from the wind. This allows ships to reduce engine power, lowering fuel consumption and CO₂ emissions.

The technology, generally known as sail propulsion, is covered by a portfolio of patents and is available in various size: eSAIL® model 1, 2 and 3. bound4blue's previous EU-backed projects such as GREENing the BLUE and the EIC Accelerator Programme fuelled the company’s growth in wind-assisted maritime technology, helping in validating initial prototypes, improving the designs, and reaching a commercial product. 

“The Innovation Fund grant was decisive in de-risking some of the first commercial retrofits and unlocking private co-investment from the shipowners,” says  says José Miguel Bermúdez Miquel, CEO of bound4blue CEO. 

“By supporting real installations on operational vessels, it helped us move beyond the pilot phase and demonstrate the viability of suction sail technology at scale. This kind of backing is essential - not just to validate innovative solutions, but to accelerate their adoption across an industry where technical, financial, and operational risks can otherwise stall progress.”

SustainSea is expected to avoid over 45 thousand tonnes of CO₂ emissions in ten years of operation. Ambitious, but possible thanks to eSAIL®, which can rotate automatically and adapt to wind conditions to deliver fuel savings of 10-20 % per voyage, with reduction peaks of over 30 % under optimal conditions. By turning wind into direct propulsion for ships, the technology allows vessels to reduce engine loads while boosting operational performance, reducing fuel consumption and lowering greenhouse gas emissions. The system is also fully compatible with new fuels being used for maritime transport.

Suction sails are rigid, wing-shaped structures that use fans to draw air through tiny holes, boosting lift and preventing stall. This allows ships to generate more thrust with smaller equipment. bound4blue’s eSAIL® matches the savings of rigid sails using seven times less surface, enabling compact, lightweight, and easy-to-retrofit installations. Suction sails work in most wind conditions - even upwind - making them a versatile solution for global shipping.

From concept to open sea

The Innovation Fund grant  was key in helping to close commercial contracts with four major shipowners: Odfjell, Louis Dreyfus Company, Eastern Pacific Shipping, and Marflet Marine. 

In early 2025, the first three eSAIL® systems were installed on the Bow Olympus, Atlantic Orchard, and Pacific Sentinel, with all three retrofitted vessels entering service between January and March 2025. At Nor-Shipping 2025 expo, performance data, confirming double-digit fuel savings in real-world conditions of these vessels were shared. Two additional installations (EPS NTS and Marflet’s Santiago I) are scheduled for the coming months, bringing the five-vessel fleet fully operational 

Transatlantic sea operations on Odfjell’s Bow Olympus confirmed the estimated GHG savings potential. In April 2025, it set sail from EDR Antwerp Shipyard in Belgium for the Port Houston in Texas. Its voyage surpassed expectations, boasting a 15-20 % energy-saving effect, and showing that sustainable deep-sea shipping is feasible. By 2026, SustainSea will complete installations on vessels.

About the Innovation Fund 

The Innovation Fund, financed by EU Emissions Trading System revenues, is one of the world’s largest funding programmes for the demonstration of innovative low-carbon technologies. The Fund focuses on highly innovative clean technologies and big flagship projects with European added value that can significantly reduce greenhouse gas emissions.  

Article published on 17 July 2025